Delayed polyurethane action catalysts

ABSTRACT

Novel salts of tertiary amines and alpha-substituted carboxylic acids have advantages as delayed action thermally activated catalysts such as in urethane and epoxy catalysis. Some salts of tertiary amines tend to dissociate reversibly when heated. However, the compounds of the present invention preferentially decompose, irreversibly, to generate carbon dioxide when heated.

United States Patent Bechara et al.

[ 1 Jan. 21, 1975 DELAYED POLYURETHANE ACTION CATALYSTS Inventors:Ibrahim S. Bechara, Boothwyn;

Dewey G. Holland, Chadds Ford, both of Pa.

Air Products and Chemicals, Inc., Wayne, Pa.

Filed: Sept. 26, 1972 Appl. No.: 292,344

Assignee:

U.S. Cl. 260/268 T, 260/2 N, 260/77.5 AC, 260/246 B, 260/247, 260/247.5R, 260/268 R, 260/293.5l, 260/309, 260/465.4, 260/501.14,260/50l.17,260/501.19, 260/50l.2l, 260/535 R Int. Cl C07d 53/00 Field of Search260/268 T, 465.4

References Cited UNITED STATES PATENTS 9/1952 Trigg et al. 260/50l.14/1957 Scudi et al..... 260/50l.2 10/1964 Sonbert 260/268 T PrimaryExaminerDona|d G. Daus Assistant Examiner-Mary C. Vaughn Attorney,Agent, or Firm-Harold A. Hormann; Barry Moyerman [57] ABSTRACT Novelsalts of tertiary amines and alpha-substituted carboxylic acids haveadvantages as delayed action thermally activated catalysts such as inurethane and epoxy catalysis. Some salts of tertiary amines tend todissociate reversibly when heated. However, the compounds of the presentinvention preferentially decompose, irreversibly, to generate carbondioxide when heated.

1 Claim, N0 Drawings DELAYED POLYURETHANE ACTION CATALYSTS BACKGROUND OFTHE INVENTION 1. Field of the Invention The invention relates to thecatalysis of urethane and epoxy resin reactions and particularly to theformation of such polymers in the form of cellular polyurethanes,polyurethane coatings, and epoxy bodies and films. The catalystcompositions comprise tertiary amine salts which decompose thermally torelease the catalytically effective tertiary amine moiety.

2. Prior Art In certain applications of polyurethanes and epoxy resins,it is desirable to prepare a composition comprising substantially all ofthe ingredients at a relatively low temperature and to bring about therapid polymerization reaction at the time when the composition is heatedto the activation temperature. When attempts are made to employ aminesas the catalyst for such heat activatable compositions, difficulties areencountered because the amine tends to significantly promotepolymerization at room temperature. Delayed reaction catalysis haspreviously been achieved by employing an acid salt of a tertiary amine.For example, a measure of delayed action catalysis has been achievedusing materials such as the benzoate salt or the acetate salt of atertiary amine. The propensity of such salts is to partly dissociate atroom temperature as well as at elevated temperatures when introduced ascatalyst in a polymer precursor system. Some dissociation occurs at roomtemperature, causing premature amine catalysis, thereby adverselyshortening the useful pot life of the composition of ingredients. Atelevated temperature reaction conditions, some of the amine has beenunavailable for catalysis because of the reversibility of thedissociation phenomena.

In the balanced catalyzation of polyurethane compositions, it has beenadvantageous to use a mixture of amine catalyst and tin catalyst.However, the lack of compatibility between the benzoate salts oftertiary amines and tin catalysts has impaired growth of use of suchcatalyst compositions. Notwithstanding the continuing demand forpolyurethane precursor composi' tions suitable for heat activatedcatalyzation, previous efforts to use the salts of tertiary amines asdelayed action catalysts encountered troublesome disadvantages.

SUMMARY OF THE INVENTION where A is an amine which contains at least onetertiary nitrogen atom;

R and R are independently H, alkyl of C -C or aryl; i

X is a decomposition promoting group selected from CN, SO, S0 CO, N0COCH CO 4;

m is an integer of l or 2;

n is 1 when X CN, N0 CO COCH and n is 2 when X C0, SO, S0

Representative compounds which may be employed as the catalyst forpolyurethane formation and which will fall in the scope of thisinvention are 066) usa e-cm HNA: H -CH2CN TEDA bis cyanoacetate 69 6 9 Eii 6 6 N/\/NH 0- -CH2-- CH2C-O HN/\/N bis TEDA acetone dicarboxylate ICH3 9 HOHQC HEC-NH o-c-ca -cn DMEA cyanoacetate on o o e on t 3 ll II ne 3 HOCH2CH2NH O-CCHgC-CIIgC-O HNCH2CH2OH (-9] bis DMEA acetone CH3 CH3dicarboxylate CH CH3 ca -g-ca c1t o ca ca g CH 32,2'oxybis-(ctimethylethylamin0)- sulfonyl diacetate b1s(dimethylcyclohexylamine) thionyl diaeetate 9 an? o-g-cn -cu si H -C-CH NO 6 u 22 CH O Alpha-substituted carboxylic acids that can be employed accordingto this invention include cyanoacetic acid, nitroacetic acid, acetonedicarboxylic acid, sulfonyl diacetic acid, thionyldiacetic acid,acetoacetic acid, benzoylacetic acid and the like.

Included in this invention are the salts of the abovedescribed acids andof amines containing one or more tertiary nitrogen atoms, morespecifically such amines include tetramethyl butane diamine (TMBDA),trimethyl amin'oethyl piperazine (TAP), tetramethyl guanidine,azabicyclo heptanes, azabicyclooctanes, N- allyl piperidines, 2,2oxybis-(morpholino ethyl ether), amidines, N-alkyl imidazoles, silylmorpholines, and the like.

The amine salts of the invention are generally prepared by mixing onemole of the amine and one mole of monobasic acid or one to two moles ofdibasic acid.

Bis-tertiary amine salts are prepared by mixing one mole of bis-tertiaryamine and one to two moles of either monobasic or dibasic acid. Whiledirect admixture 'of the amine and acid is possible it is preferred touse a solvent. Solvents that can be used include water, alcohols,ethers, or acetone. The preferred solvent is acetone. The temperaturerange of the reaction is between -50C. When reaction is complete theproduct salt is separated from the solvent as by filtration, centrifug-N -ethyl morpho line eyanoac'etate N,N Dimethyl isopx'opanol amineaceto- -acetate N- methyl sil yl morpholino cyanoacetate N, Ndimethylpiper'azine bis nit roacetate or the solvent may be removedby'evaporation under reduced pressure where the product salt is aliquid. It is understood that the amine salts of the invention includethe hydrates as, well as the anhydrous forms. Thus, the product saltrecovered from preparation in water-containing solvent may be in thehydrous form; or the anhydrous salt may be hydrated at or prior to itsuse as the activator-catalyst.

Because of this careful selection of the alphasubstituted carboxylicacid components of the amine salt, the amine salts undergo irreversiblethermal decomposition at the temperature of activation as shown inreaction 2 instead of merely dissociating in a reversible manner asshown in reaction 1.

Reaction 1 9 e a I I CH -C -0 HA jCH -C -OH+A Reaction 2 (39 e X-CH C -0T XCH3+A+CO2 where A is an amine containing at least one tertiarynitrogen atom and X is as hereinbefore described.

The rapid, irreversible thermal decomposition of the acid component ofthe salt at the activation temperature liberates the tertiary amine foreffective catalyzation of the aromatic or aliphatic polyisocyanate andpolyol precursors, or epoxy precursor at the activation temperature.Thus the precursor formulation for the polyurethane or epoxy resin cancontain the catalytic components comprising the salt of the tertiaryamines at room temperature and maintain a prolonged shelf life and/or aprolonged pot life, notwithstanding the susceptibility of thedecomposition for activation by the elevated temperature.

The proposed catalysts of the invention can be used solely as anactivator for polyurethane or epoxy resin formation or as co-catalystswith other known catalysts, be it an amine catalyst or an organometallic catalyst such as those derived fromm tin, silicon, antimony,lead, copper, iron or the like.

The compounds of the invention can also be used to an advantage inpolyurethane formulations or epoxy resin precursors where blowingagents, pigmentation, fillers, surfactants and other additives arepresent.

The invention is further clarified by reference to a plurality ofexamples.

EXAMPLE I A solution of 100 ml of acetone containing 0.2 mole ofcyanoacetic acid was mixed with 100 ml of acetone containing 0.1 mole oftriethylenediamine. The mixture of the two solutions led to theformation of a precipitate consisting of triethylenediamine biscyanoacetate having a formula This precipitate was dried in a vacuumoven at 60C. Its melting point was established at 124C. Analysisconfirmed that the composition was the expected bis triethylenediaminedicyanoacetate.

Calculated Found C 51.06 C 50.72 H 6.38 H 6.32 N 19.86 N 19.49

In a similar manner, triethylenediamine monocyan oacetate was prepared.It too decomposed in the sublimer at l35-l40. The analysis for C l-1 N Owas as follows:

Calculated Found 54.82 54.50 H 7.61 H 8.50 N 21.32 N 20.35

Table 1 Curing time at 100C using NCCH CO H.N(C l l N.HO CCH,CN

grams catalyst minutes for cure The same triethylenediamine biscyanoacetate was evaluated as a curing agent of said coating prepolymermaintained at room temperature. Data relating to the uniformity of curetime notwithstanding variations in the amount of triethylenediamine biscyanoacetate catalyst employed are shown in Table 2.

Table 2 Curing time at room temperature using NCCH CO H.N(C H NHO CCH CNgrams hours As a control, a solution containing essentially 33 percenttriethylenediamine in polypropylene glycol was employed as a comparisoncatalyst; also employing the same polyester urethane precursor in 10gram lots. There was a significant variation in the curing timedependent upon the concentration of the catalyst both at roomtemperature and at 100C, as shown in Tables 3 and 4.

Table 3 Curing time at room temperature using 33% solution of N(C H Ngrams hours Table 4 Curing time at 100C using 33% solution of N(C H,) N

grams minutes EXAMPLE n The decomposition temperature andcharacteristics of the triethylenediamine bis cyanoacetate wasinvestigated by heating a 3.4 gram sample of the salt in a sublimerthroughout a temperature range from 130 to 150C, that is, above themelting point of 124C. The gas evolved from the sublimer was passedthrough a gas bulb and into a gas meter. The evolved gas was identifiedas carbon dioxide by passage through a solution of barium hydroxide,whereby a white precipitate of barium carbonate was formed. After thedecomposition of the salt, the residue was weighed and was found to be1.30 grams, and was identified as triethylenediamine. The theoreticalvolume of gas 0.019 cu. ft., corresponded closely to the gas volumemeasured, 0.018 cu. ft. The measured weight of triethylenediamine as1.30

gram closely corresponded to the theoretical amount of 1.34 gram.

It is to be understood that the terms decomposition temperature" andthermal activation temperature are not synonymous in that the onset ofdecomposition of such salts is generally at a lower temperature than thedecomposition temperature and progresses through an increasingtemperature range. When employed as catalyst such salts at elevatedtemperature decompose and start an exothermic reaction in thepolymerization which in turn promotes further decomposition of thecatalytic salt.

EXAMPLE III In a combination G.C. Mass Spectrometer instrument where theG.C. is equipped with 15 ft. chromatographic column packed with 15percent Apiezon L on Gas Chromatograph Q substrate, several aqueous ormethanolic solutions of the claimed salts were injected in the G.C. at150C and the temperature of. the column programmed from 100200C.

The decomposition products of the salt were separated on the column thenpassed to the mass spectrometer by which they were identified. Thefollowing table summarizes the results obtained.

TABLE-Continued Approximate Thenas determined reti- Decomposition fromgas cal Salt Products chromatography wt.%

TEDA thionyl co V 42.4 31.7 diacetate DMSO 3.0 28.0 TEDA 53.4 40.3

EXAMPLE W A polyurethane precursor formulation containing 100 grams ofpolypropylene glycol having a molecular weight of about 3000, andmarketed as CP-3000 was employed as the polyol. The precursor alsocontained 10 grams of a technical grade of tolylene diisocyanatecomprising about an to 20, 2,4- to 2,6-isomer ratio. At roomtemperature, the use of triethylenediamine bis cyanoacetate showed thesame degree of cure during a 48 hour period in a series of tests usingincreasing amounts of the catalyst, thus indicating that the curing wasoccurring spontaneously and not by reason of the catalyst concentration.At C curing time was greatly shortened over the uncatalyzed formulation,the effect of catalyst concentration upon curing time was essentiallythe same using either the solution of the triethylenediamine or thetriethylenediamine bis cyanoacetate salt. At a concentration of 0.1grams of catalyst per 10 grams of precursor, the curing time was 14minutes for both the decomposable salt and for the solution oftriethylenediamine. Using 0.20 grams of catalyst per 10 grams ofprecursor, the curing time was 12 minutes for the decomposable salt, and8 minutes for the solution of triethylenediamine. Using 0.4 grams ofcatalyst per 10 grams of precursor, the curing time was 8 minutes forthe salt of triethylenediamine bis cyanoacetate and was 6 minutes forthe solution of triethylenediamine. At room temperature, the curingtimes with the solution of triethylenediamine were 100, 60, 30, and 20minutes for the quantities of0.12, 0.24, 0.36 and 0.48 grams ofcatalyst, respectively, for 10 grams of polyurethane precursor. I

Such data established that the triethylenediamine bis cyanoacetate is aneffective delayed acting catalyst which can be activated by heat andprovide the reliable and practical performance associated with a freetriethylenediamine catalyst.

EXAMPLE V A series of compounds having the desired easy decomposabilitywas prepared from several acids and tertiary amines. The preparationswere carried out in a round bottomed flask equipped with a refluxcondenser and a mechanical stirrer by adding the equivalent amount ofthe amine needed to the acetone solution of the acid in the flask. Thetemperature of the reaction was maintained below 50C by means ofexternal cooling. After the addition was completed the reaction mixturewas cooled and the product isolated by filtration. The yields werequantitative.

After drying in vacuum oven the purity and the composition of the saltwere confirmed by chemical analysis. The novel catalysts thus preparedincluded:

Amine Empirical formula m.p. C. Analysis Calc. Found Triethylenediaminethionyldiacetate C l-l O S N 103 C,43.52 C,43.l7 H, 6.70 H, 6.47 N.l0.l2N,l0.07 4-(2-dimethylaminoethyllmorpholine bis cyanoacetate C H ,N O 74C5 1 .22 (.5 l .25 H. 7.32 H. 7.43 N.l7.07 N,l6,96

EXAMPLE VI ofthe advantageous delayed action and long stability of About100 parts of polyol mixture consists of about equal parts ofpolypropylene glycol having a molecular weight of about 2000 and apolyethylene glycol having a molecular weight of about 4000. Theprecursor contains about 12 grams tolylenediisocyanate per 100 gramspolyol and 4 grams of triethylenediamine bis cyanoacetate. The precursoris employed in a coating machine in which a strip of fabric advancingthrough a coating zone is given a uniform thin coating of precursor. Thecoated fabric advances into zones in which the precursor undergoes thecreaming, foaming, rising, and curing steps to bond the polyurethanefoam coating onto the advancing fabric. The curing zone is maintained at100C, from which zone is withdrawn a cured polyurethane foam coatedfabric. The precursor is maintained at substantially room temperature.It is important that the precursor have a long pot life so that thereare not troublesome increases in the viscosity of the precursor duringnormal operations. The tertiary. amine salt is prepared by the mixing ofthe triethylenediamine and sulfonyldiacetic acid in acetone and the.filtration of the salt from the acetone. Using such salt as the catalystthe delayed action of the catalyst is quite satisfactory, a good productbeing obtained because of the decomposition of the salt, asdistinguished from the mere dissociation of the salt occurring in acontrol using triethylenediamine diacetate salt.

EXAMPLE VI] A fabric having a polyurethane foam coating is prepared byusing as the catalyst a mixture of 0.40 parts of catalyst per parts ofpolyol, composed of 100 parts of ethylene glycol terephthalate, M.W.3000, parts of di(isocyanato-chlorophenyl)methane. The amine catalystbeing the triethylenediamine acetone dicarboxylate in which the twoacetyl groups are joined together by a carbonyl group. Such delayedaction catalyst provides results superior to those obtained using adibenzoate salt of triethylenediamine as the thermally activatablecatalyst. The ease of thermal decomposition of the acetone dicarboxylateanion, and the minimized propensity for reversible dissociation of theamine salt are believed to be at least a partial explanation for thesuperior results.

EXAMPLE VIII The delayed action catalyst is the salt of hisdimethylamino ethylether and thionyl diacetic acid. A small amount ofdibutyltindiacetate catalyst constituting about US as much as the aminecatalyst is employed in the precursor, which contains l00 parts ofethylene glycol terephthalate, M.W. 3,000, 20 parts of di(isocyanato-chloro-phenyl)methanc. 2.5 parts of the amine salt and 0.5 parts ofdibutyltin diacetate. The polyurethane foam coated fabric production issatisfactory because the catalyst precursor mixtures.

EXAMPLE IX In the curing of an epoxy resin, a mixture of 10 parts ofglycidyl polyether (Epon 828) and 1 part of amine curing agent wasstirred for 2 minutes then allowed to cure at various temperatures. Thefollowing table gives comparative cure times for triethylenediamine andtriethylenediamine bis cyanoacetate salt.

Cure Temperature C. Cure Time in Minutes TEDA bis TEDA cyanoacetate RT.420 week 50 48 l l l00 8 55 l35 3 l2 l50 l 8 Clearly this table showsthat for applications where extended pot life is desirable the compoundof the invention offers great advantage while exhibiting fully practicalactivity upon thermal activation.

EXAMPLE X Reversible Cure time in min. Cure time in Amine Salt conc. atroom temp. minutes at 100C TEDA diformate 0.08 I3 0.18 65 9 0.23 45 60.30 30 5 These room temperature data show the TEDA diformate affordsonly short pot life in contrast with the salts of the invention, such asillustrated in Example I, Table 2.

EXAMPLE XI A prepolymer mix composed of parts polyol CP 3000 and 10parts 80/20 TDI was cured by varying amounts of triethylenediamine bisacetate (a reversible salt) both at room temperature and at 100C. Thefollowing table summarizes the cure time in minutes vs. concentration.

Conc. Cure time in Cure time in Amine salt pph. minv at RT. minutes at100C TEDA bis acetate 0.08 106 0.17 51 6 0.33 36 4 Where roomtemperature data show the triethylenel. A salt of triethylenediamine andcyanoacetic acid.

1. A SALT OF TRIETHYLENDIAMINE AND CYANOACETIC ACID.